Due to the increasing cost pressure, a reliable wind turbine (WT) is a major priority. Reliability is strongly determined by the design process. Therefore, it is required to have accurate and reliable load assumptions, ideally at early stages of the design process. This contribution discusses suitable simulation methods and then presents the validation of the load calculation of a full scale multi-body simulation (MBS) wind turbine model. The modelled wind turbine is a 2.75 MW generic research wind turbine. The aim of the MBS model is to produce load time series of components’ internal loads and states. These results are used as input for more detailed component models e.g. finite element (FE) tooth contact or bearing models. Subsequently these are then used to calculate detailed bearing and tooth loads. The MBS is compared with comprehensive measurements from a full scale 4 MW system test bench. The main focus will be on the validation of the MBS models internal components loads, displacements and deformations on which the bearing and tooth loads depend on. It is evaluated which model parameters influence these calculation objectives as well as the modelling methods and fidelity required to represent them meaningfully. It is evaluated that model and test indicated comparable results.